There's an argument to be made in favour of holding off until the results of 2020 come in. If Biden takes it then, although he shares what is now the general American aim of containing China, he might not be willing to toss US companies into the furnace to do it. He'll probably take the TPP/alliance-building route (which suits China just fine, it's what it has been dealing with for the past 30 years).
If Trump wins or if his successor proves as insane, then by all means scorch the Earth.
In all cases, I believe it is now crystal clear to all Chinese policymakers that technological self-sufficiency is now priority #1 through 99. Xi himself has spoken about this on numerous occasions.
The CCP is a technocratic government, and it must be responsive to economic conditions and public opinion. Throwing Apple out would put hundreds of thousands of Chinese workers out of work, at the very least. Unlike America, China isn't on its way down and doesn't want to set itself on fire so the flames lick its enemy.
